File转换为MultipartFile工具类

 package cn.com.utils;

 import org.apache.commons.fileupload.FileItem;
 import org.apache.commons.fileupload.disk.DiskFileItemFactory;
 import org.springframework.util.FileCopyUtils;
 import org.springframework.web.multipart.MultipartFile;
 import org.springframework.web.multipart.commons.CommonsMultipartFile;

 import javax.activation.MimetypesFileTypeMap;
 import java.io.ByteArrayInputStream;
 import java.io.File;
 import java.io.InputStream;
 import java.io.OutputStream;

 public class FileToMultipartFileUtil {

     public static MultipartFile toMultipartFile(String fieldName, File file) throws Exception {
         DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory();
         String contentType = new MimetypesFileTypeMap().getContentType(file);
         FileItem fileItem = diskFileItemFactory.createItem(fieldName, contentType, false, file.getName());
         try (
                 InputStream inputStream = new ByteArrayInputStream(FileCopyUtils.copyToByteArray(file));
                 OutputStream outputStream = fileItem.getOutputStream()
         ) {
             FileCopyUtils.copy(inputStream, outputStream);
         } catch (Exception e) {
             throw e;
         }
         MultipartFile multipartFile = new CommonsMultipartFile(fileItem);
         return multipartFile;
     }

     public static MultipartFile toMultipartFile(String fieldName, String fileName, byte[] fileByteArray) throws Exception {
         DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory();
         String contentType = new MimetypesFileTypeMap().getContentType(fileName);
         FileItem fileItem = diskFileItemFactory.createItem(fieldName, contentType, false, fileName);
         try (
                 InputStream inputStream = new ByteArrayInputStream(fileByteArray);
                 OutputStream outputStream = fileItem.getOutputStream()
         ) {
             FileCopyUtils.copy(inputStream, outputStream);
         } catch (Exception e) {
             throw e;
         }
         MultipartFile multipartFile = new CommonsMultipartFile(fileItem);
         return multipartFile;
     }

 }